Extendable ramp assembly for detecting an obstruction and responding thereto

Abstract

An extendable ramp assembly includes a chassis, a first ramp slidably movable relative to the chassis and hingably connected to the chassis, and a second ramp carried by the first ramp and movable relative to the chassis and the first ramp. Separate structure is provided for extending and retracting both the first and second ramps. A first mechanism is provided for detecting whether either or both of the first and second ramps abuts an obstruction when at least one of the ramps is being extended. A second mechanism is provided for stopping the extension of at least one of the ramps or for retracting at least one of the ramps in the event of the detecting mechanism detecting the obstruction.

What is claimed is:  
     
       1. An extendible ramp assembly for use with a vehicle comprising: 
       i) a cassette attachable to a vehicle and provided with a closable access slot;  
       ii) a first ramp contained by the cassette, the first ramp being slidably movable relative to the cassette and hingably connected to the cassette;  
       iii) a second ramp contained within the first ramp and movable relative to the cassette and the first ramp;  
       iv) electric motor means for extending and retracting the first ramp through the access slot and relative to the cassette;  
       v) means for extending and retracting the second ramp relative to the first ramp and the cassette;  
       vi) a control unit for controlling the operation of the electric motor means and the means for extending and retracting the second ramp;  
       vii) means for detecting the current drawn by the electric motor means to ascertain when the current drawn exceeds a predetermined value indicative of a condition in which the first and second ramps encounter an obstruction when being extended;  
       viii) means responsive to the current detecting means for causing the control unit to stop the extension of the first and second ramps when the detecting means detects said excess current;  
       ix) means for further detecting when the first and second ramps are fully extended and operational and;  
       x) means responsive to the further detecting means for stopping the extension of the first and second ramps when the further detecting means detects the ramps are fully extended.  
     
     
       2. An extendible ramp assembly as claimed in  claim 1  wherein the means responsive to the current detecting means further causes the control unit to retract the first and second ramps when the detecting means detects said excess current. 
     
     
       3. An extendible ramp assembly as claimed in  claim 1  wherein the second ramp is resiliently biased against a switch such that when the load on the means for extending and retracting the second ramp exceeds a predetermined value the switch is activated. 
     
     
       4. An extendible ramp assembly as claimed in  claim 3  further comprising means responsive to the switch for causing the control unit to stop the extension of the second ramp when the switch is activated. 
     
     
       5. An extendible ramp assembly as claimed in  claim 3  further comprising means responsive to the switch for causing the control unit to retract the second ramp when the switch is activated. 
     
     
       6. An extendible ramp assembly as claimed in  claim 1  and further comprising means for extending and retracting the first and second ramps manually. 
     
     
       7. An extendible ramp assembly as claimed in  claim 6  further comprising a tool for facilitating the use of means for extending and retracting the first and second ramps manually. 
     
     
       8. An extendible ramp assembly as claimed in  claim 7  wherein means for extending and retracting both the first and second ramps include a feed nut and a lead screw and means for extending and retracting the first and second ramps manually comprise dogs. 
     
     
       9. An extendible ramp assembly as claimed in  claim 1  and further comprising at least one resiliently biased flap connected to the cassette and biased so as to close the access slot so as to reduce the step between the first ramp and the cassette when the first ramp is in the extended position and to close the slot when the first and second ramps are in the fully retracted position. 
     
     
       10. An extendible ramp assembly as claimed in  claim 1  and further comprising means for detecting the condition of a vehicle, in which the ramp assembly is installed. 
     
     
       11. An extendible ramp assembly as claimed in  claim 10  further comprising means responsive to the condition detecting means for causing the control unit to stop the extension of the first and second ramps when the detecting means detect the vehicle is in a certain condition. 
     
     
       12. An extendible ramp assembly as claimed in  claim 10  further comprising means responsive to the condition detecting means for causing the control unit to activate a warning signal.